What Is the Most Commonly Diagnosed Cancer in Korea? (As of 2026)

The most commonly diagnosed cancer in Korea is thyroid cancer. More than 35,000 cases were diagnosed in a single year (2023) alone, and because ultrasound screening is so widespread, a high proportion of cases are caught while still small.

Key Takeaways

• In 2023 alone, Korea diagnosed more than 35,000 cases of thyroid cancer (National Cancer Registration Statistics).
• Thyroid cancer's 5-year relative survival rate is 100.2%, meaning survival is no different from that of the general population of the same age (National Cancer Registration Statistics, 2019–2023).
• One reason thyroid cancer is so common is that ultrasound exams are widely used in Korea, making it easy to detect even small nodules.
• Stomach cancer (5-year survival 78.6%), lung cancer (42.5%), and prostate cancer (96.9%) are also cancers for which Korea has accumulated extensive surgical and treatment experience.
• Survival rates are national aggregate statistics and are not numbers that predict any individual's outcome.

Why Is Thyroid Cancer Detected So Often?

• Because neck ultrasound is a common part of health checkups, even small, symptomless nodules are easily found.
• If a thyroid nodule is felt or detected on a checkup, neck ultrasound is used to check its shape, size, and location, and if cancer is suspected, a fine-needle aspiration cytology (FNA) test is done to collect cells for confirmation.
• Papillary and follicular carcinoma, which make up the majority of thyroid cancers, tend to have a favorable course, but medullary and anaplastic thyroid cancer behave very differently — so they should never be lumped together under the same statistics.

Does Detection Mean Surgery Right Away?

• If the tumor is 1cm or smaller, confined within the thyroid, not located in a high-risk position, and shows no lymph node metastasis, active surveillance — regular ultrasound monitoring without immediate surgery — is one of the standard options.
• If the tumor grows or new findings appear during monitoring, the plan shifts to surgery at that point.
• When surgery is needed, a lobectomy (removing only one lobe of the thyroid) is often sufficient if the tumor is confined to one side; a total thyroidectomy is performed if the tumor is large, affects both sides, or has spread to lymph nodes.
• After a total thyroidectomy, patients take thyroid hormone replacement for life, but after a lobectomy, the remaining lobe often produces enough hormone that some patients can go without medication.

How Does This Compare With Other Cancers?

• Stomach cancer had a 5-year relative survival rate of 78.6% for 2019–2023 (National Cancer Registration Statistics), and when caught early, many cases can be resolved with endoscopic resection alone.
• Lung cancer's 5-year survival rate is 42.5%, up 30 percentage points from 1993–1995, with biomarker-guided targeted therapy and immunotherapy now established as standard treatment (National Cancer Registration Statistics).
• Prostate cancer has a 5-year survival rate of 96.9%; because it often progresses slowly, it is one of the rare cancers for which watchful waiting is included among the standard options.
• Diagnosis frequency, disease course, and treatment focus vary enormously from one cancer type to another, so the figures for any single cancer cannot be used to judge the overall picture.

FAQ — Does a high diagnosis rate for thyroid cancer mean it's dangerous?

No. Thyroid cancer's 5-year relative survival rate is 100.2%, showing virtually no difference in survival compared with the general population — a level comparable to the U.S. SEER statistic of 98.3% (2016–2022). A high detection rate mainly reflects how widespread ultrasound screening is, catching cancers even at a small size. The real focus of treatment is less about survival and more about the extent of surgery, scarring, and hormone management.

FAQ — Can Korea's robotic/endoscopic surgery treat thyroid cancer without visible scarring?

Yes — robotic and endoscopic thyroidectomy approached through the armpit, around the areola, or through the mouth can avoid leaving a scar on the neck, and Korea has extensive experience performing this type of surgery. However, it is only an option if the tumor's size, location, and extent of lymph node spread meet certain criteria, so individual ultrasound findings need to be reviewed.

Sources and Notes

• This article was written based on the National Cancer Registration Statistics 2019–2023 (Korea Central Cancer Registry, National Cancer Center), SEER 2016–2022, and patient guidelines from the National Cancer Information Center and NCCN.
• This content is intended to provide general medical information, and actual diagnosis, treatment methods, and outcomes may vary depending on individual circumstances. Accurate diagnosis and treatment decisions should always be made in consultation with a medical professional.